Line Contactor for VFD Question.

So I'm really newbie in VFD and automation stuff. That being said, I do have an understanding of electrical devices in general. Now my question: What are the reasons ppl are using contactor for VFD on the line side instead of something like DPST Circuit Breaker?
My initial assumption is that they can turn it on with just a simple button that will close the relay on the AC line. The contactor would also allow the possibility of logic control. That being said, I am not sure if that is the whole picture of the implementation of the contactor on the VFD line side. Would you be able to tell me other reasons for doing so, and if my initial assumption is wrong.
P/s: Are there also any safety-related reasons? I couldn't really think of one on top of my head.

Not every VFD is rated as a motor controller, some are. So there is the chance of connecting thermal sensors, etc in with the contactor to kill power in case of overloads etc.

VFDs with an "STO" connection (safe torque off) can be pretty positively disconnected in such a case, but many cannot. The STO disconnects power to the gate drives, so the IGBTS simply cannot be driven. You can still get DC faults if the VFD has a bad IGBT or two, , but nothing that can turn the motor.

There may be other safety reasons as well, such as an external safety circuit for the machine that needs to shut it off due to some totally other fault elsewhere. Commanding the VFD to stop may not be considered good enough.

How about the AC input power to the VFD? I saw that some people will connect the hot or hot and neutral through a contactor. Besides a reason of being easier to turn on or off, I couldnt think of a reason why ppl do so, and I wonder if it is good practice for me to follow. Im running my 1hp VFD through a DPST Circuit Breaker atm.

dk4one said:

How about the AC input power to the VFD? I saw that some people will connect the hot or hot and neutral through a contactor. Besides a reason of being easier to turn on or off, I couldnt think of a reason why ppl do so, and I wonder if it is good practice for me to follow. Im running my 1hp VFD through a DPST Circuit Breaker atm.

Click to expand...

Isn't that what you asked? Contactor on AC input?

It does not have to be a good idea unless you have a need such as I mentioned.

In general you do need a "disconnect" between the machine (or its controller) and the power source. "Disconnects" are capable of being locked-out, which a breaker or contactor may not be. Can be a plug and receptacle, or if hard-wired, a regular lever operated non-fused disconnect switch.